Silicon-containing polymer, process for its production, resist composition employing it, pattern-forming method and electronic device fabrication method

ABSTRACT

A silicon-containing polymer having a tetrafunctional siloxane portion as the basic skeleton, and containing a carboxylic acid group-containing triorganosiloxane portion and a carboxylic acid derivative group-containing triorganosiloxane portion in a specific proportion. It may be advantageously used as a negative non-chemical amplification resist polymer or a positive chemical amplification resist polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Division of application Ser. No. 09/553,479 filed Apr. 20,2000, now U.S. Pat. No. 6,342,562 the disclosure of which is herebyincorporated by reference herein in its entirety.

This application is based upon and claims priority of Japanese PatentApplications No. Hei 11-116517, filed Apr. 23, 1999, and No. 2000-82613,filed Mar. 23, 2000, the contents being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a silicon-containing polymer and aprocess for its production. In particular, the invention relates to asilicon-containing polymer that is useful as a primary agent in a resistmaterial composition that provides intricate resist patterns by exposureto radiation with ArF excimer laser light, an electron beam or the likefollowed by development with an alkali developing solution, and to aprocess for its production. The invention further relates to a resistcomposition containing such a polymer, to a method of forming resistpatterns using it, and to a method of fabricating electronic devicesincluding LSIs, magnetic heads, liquid crystal devices, MCMs, etc. andphotomasks using the method.

2. Description of the Related Art

With the trend toward higher integration and higher functionality ofelectronic devices, such as semiconductor devices, in recent years,progress continues to be made toward more intricate and multilayeredwirings. In the manufacture of second generation semiconductor deviceswith ever higher integration and higher functionality, research hasbegun on using ArF excimer lasers and EUV light as exposure lightsources in lithography techniques for intricate working, and progress isbeing made toward shorter wavelength applications. Problems raised withshorter wavelength light sources include the transmittance of the resistmaterials and reflection from the substrates, but surface imaging hasbeen proposed as an effective technique to counter these problems, and aparticularly effective method is the bi-layer resist method employingsilicon-containing polymers as resist materials.

According to the bi-layer resist method, an organic resin is coated to afilm thickness of 1 μm, for example, to form a lower resist layer onwhich there is formed an upper resist layer of a thin film of about0.1-0.2 μm, and then the upper resist layer is first patterned by lightexposure and development of the upper layer and the resulting upperlayer pattern is used as a mask for etching of the lower layer, to forma resist pattern with a high aspect ratio. The bi-layer resist methodcan alleviate or prevent the influence of level differences in thesubstrate and reflection from the substrate surface by the lower layerresist, while the small film thickness of the upper layer resist allowsimproved resolution compared to single-layer resist methods.Consequently, the bi-layer resist method is more advantageous than thesingle-layer resist method for formation of intricate patterns onsubstrates with large level differences and it is therefore believed tobe a more effective resist process for the shorter wavelengths ofexposure light sources which will be used in the future.

Bi-layer resist materials employing various silicon-containing polymershave been reported to date (for example, Japanese Unexamined PatentPublications SHO No. 58-96654, No. 61-108628, No. 62-104032 and No.62-220949, Japanese Unexamined Patent Publications HEI No. 1-56732, No.1-222254, No. 3-29311, No. 5-58446, No. 5-181280, No. 6-95385, No.6-184311, No. 6-202338 and No. 11-130860), but none of those availablehave been excellent for alkali development in terms of shelf-life,sensitivity, resolution, O₂-RIE resistance, heat resistance, or shorterwavelengths of exposure light sources for pattern intricacy. Inparticular, none have exhibited excellent developing properties in a2.38% tetramethylammonium hydroxide (TMAH) aqueous solution, which iscurrently a commonly used alkali developing solution for mass productionof LSIs, and this has been a drawback against their application togeneral purpose developing equipment.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the drawbacks ofthe prior art described above by providing a silicon-containing polymerwhose production is simple, which exhibits an excellent shelf-life,which is suitable as a resist material that can be easily developed withcommon alkali developing solutions, and which simultaneously provideshigh sensitivity, high resolution, high O₂-RIE resistance and high heatresistance.

It is another object of the invention to provide a silicon-containingpolymer, a process for its production, a negative non-chemicalamplification resist composition or chemical amplification resistcomposition containing it, a resist pattern-forming method employing thecomposition, and a fabrication method for electronic devices andphotomasks that employs the method.

As a result of much diligent research aimed at achieving theaforementioned object, the present inventors have found that theproblems described above can be solved by using a silicon-containingpolymer with a specific proportion of functional groups.

Thus, the present invention provides a silicon-containing polymerincluding the structure represented by formula 1 below as a mainstructural unit.

where R¹ represents a monovalent organic group, R² represents a directbond or a divalent organic group, R³ represents a monovalent organicgroup or an organosilyl group, any of which groups may be of differenttypes, X represents hydrogen, a monovalent organic group or anorganosilyl group, which groups may be of different types, k and l arepositive integers, m and n are 0 or positive integers, and thesesubscripts satisfy the following relationship.$0 < \frac{1}{1 + m + n} \leqq {0.8\quad 0} \leqq \frac{m}{1 + m} < 0.2$

That is, in formula 1, the ratio of the carboxylic acid group-containingtriorganosiloxane portion and the carboxylic acid derivativegroup-containing triorganosiloxane portion is restricted, as representedby l and m. When a silicon-containing polymer according to the inventionhaving the structure of formula 1 as the main structural unit is used asa negative non-chemical amplification resist, the carboxylic acidgroup-containing triorganosiloxane portion confers alkali solubility,thus affecting the solubility and resolution in alkali developingsolutions, and consequently it must be present in a prescribed amount.Similarly, since the carboxylic acid derivative group-containingtriorganosiloxane portion has an adverse effect of lowering the alkalisolubility and resist resolution, its content is also restricted. Forthis reason, the carboxylic acid group-containing triorganosiloxaneportion and the carboxylic acid derivative group-containingtriorganosiloxane portion are present in a specific proportionrepresented by the relational equality given above.

The invention also provides a resist composition containing asilicon-containing polymer of the invention having the structure offormula 1 as the main structural unit. The resist composition isprimarily a negative non-chemical amplification resist composition. Theresist composition may contain one or more different silicon-containingpolymers of the invention having the structure of formula 1 as the mainstructural unit, and if necessary it may also contain other desiredpolymers or compounds.

The invention also provides a silicon-containing polymer including thestructure represented by formula 3 below as a main structural unit.

where R¹ represents a monovalent organic group, R² represents a directbond or a divalent organic group, R⁷ and R⁸ each independently representa monovalent organic group or an organosilyl group, any of which groupsmay be of different types, X represents hydrogen, a monovalent organicgroup or an organosilyl group, which groups may be of different types, kand q are positive integers, l, n and p are 0 or positive integers, andthese subscripts satisfy the following relationship.$0 \leqq \frac{l}{l + n + p + q} < {0.5\quad 0.1} < \frac{q}{l + n + p + q} \leqq 0.8$

That is, in formula 3, the ratio of the carboxylic acid group-containingtriorganosiloxane portion and the carboxylic acid derivativegroup-containing triorganosiloxane portions is restricted, asrepresented by l, p and q. When a silicon-containing polymer accordingto the invention having the structure of formula 3 as the mainstructural unit is used as a positive chemical amplification resist, thecarboxylic acid group-containing triorganosiloxane portion exhibitsalkali solubility such that the non-exposed sections dissolve duringdevelopment, and therefore its content is restricted. Similarly, thecarboxylic acid derivative group-containing triorganosiloxane portion(q) has a functional group that is eliminated by acid catalysts or whennecessary heating, and this elimination reaction occurring at theexposed sections gives a resist pattern. Since the carboxylic acidderivative group-containing triorganosiloxane portion (p) that does notundergo elimination by the action of acid or the like has an adverseeffect of lowering the alkali solubility and resist resolution, itscontent is also restricted. For this reason, the carboxylic acidgroup-containing triorganosiloxane portion and the two differentcarboxylic acid derivative group-containing triorganosiloxane portionsare present in a specific proportion represented by the relationalequality given above.

The invention also provides a resist composition containing asilicon-containing polymer of the invention having the structure offormula 3 as the main structural unit. The resist composition maycontain one or more different silicon-containing polymers of theinvention having the structure of formula 3 as the main structural unit,and if necessary it may contain an acid generator or if necessary it mayalso contain other desired polymers or compounds.

The resist composition of the invention may be used either in asingle-layer resist method or in a bi-layer resist method.

One resist pattern-forming method according to the invention comprisesusing a resist composition of the invention to form a resist layer on aworking substrate, and forming a resist pattern by light exposure anddevelopment of the resist layer.

Another resist pattern-forming method according to the invention is amethod of using a first resist material to form a lower resist layer ona working substrate, using a second resist material to form an upperresist layer thereover, patterning the upper resist layer by lightexposure and development, and etching the lower resist layer using theresulting upper layer pattern as a mask to form a resist pattern, and itcomprises the use of a resist composition according to the inventiondescribed above as the second resist material.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1, FIG. 2 and FIG. 3 are illustrations of a method of forming agate wiring pattern using a resist composition according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The silicon-containing polymer of the invention is particularly usefulas a base resin for a resist composition, and it includes atetrafunctional siloxane portion as the skeleton and a triorganosiloxaneportion having a carboxylic acid group as an alkali-soluble group. Itmay also include, in addition to these, other functional groupsaffecting the polymer properties, on which there are no particularrestrictions so long as they are monovalent or divalent organic groups.

However, in general formula 1, k and l are positive integers, m and nare 0 or positive integers, and these subscripts satisfy the followingrelationship.$0 < \frac{1}{1 + m + n} \leqq {0.8\quad 0} \leqq \frac{m}{1 + m} < 0.2$

That is, the ratio of the carboxylic acid group-containingtriorganosiloxane portion and the carboxylic acid derivativegroup-containing triorganosiloxane portion is restricted.

In formula 1, the compositional ratio of the carboxylic acidgroup-containing triorganosiloxane portion (l) with respect to all ofthe terminal functional group units (l, m, n) other than thetetrafunctional siloxane skeleton (k) must be larger than 0, and nogreater than 0.8. If this ratio is 0 the alkali solubility of thepolymer is lost, so that it will not function as a negative non-chemicalamplification resist. If it is greater than 0.8, the alkali solubilitywill be too high, making it difficult to obtain a pattern by developmentwith the 2.38% TMAH aqueous solution used for ordinary intricateworking. The compositional ratio of the carboxylic acid derivativegroup-containing triorganosiloxane portion (m) of the carboxylic acidgroup-containing triorganosiloxane portion and carboxylic acidderivative group-containing triorganosiloxane portion (l, m) must be 0or greater and smaller than 0.2. The carboxylic acid derivativegroup-containing triorganosiloxane portion (m) is a cause of reducedresist performance in terms of alkali solubility and resist resolution,and it is preferably absent for use as a negative non-chemicalamplification resist, while the upper limit of 0.2 can ensure resistperformance. According to the invention, it was found that for inhibitedproduction of the carboxylic acid derivative group-containingtriorganosiloxane portion (m), it is effective to use tetraethoxysilaneas the starting monomer for formation of the polymer skeleton duringproduction of the silicon-containing polymer of the invention, and touse a carboxyl group-containing compound that does not react with thestarting silicone monomer or the resulting silicon-containing polymerduring production of the polymer. A low molecular weight carboxylgroup-containing compound is preferred as the carboxyl group-containingcompound, and acetic acid, acetic anhydride and the like areparticularly preferred for use.

In formula 3, k and q are positive integers, l, n and p are 0 orpositive integers, and these subscripts satisfy the followingrelationship.$0 \leqq \frac{l}{l + n + p + q} < {0.5\quad 0.1} < \frac{q}{l + n + p + q} \leqq 0.8$

That is, the ratio of the carboxylic acid group-containingtriorganosiloxane portion and the carboxylic acid derivativegroup-containing triorganosiloxane portion is restricted.

In formula 3, the compositional ratio of the carboxylic acidgroup-containing triorganosiloxane portion (l) with respect to all ofthe terminal functional group units (l, n, p, q) other than thetetrafunctional siloxane skeleton (k) must be 0 or greater, and smallerthan 0.5. If this ratio is 0.5 or greater the alkali solubility of thepolymer is increased, resulting in dissolution of the non-exposedsections. The compositional ratio of one carboxylic acid derivativegroup-containing triorganosiloxane portion (q) with respect to theterminal functional group units (l, n, p, q) must be greater than 0 andno greater than 0.8. Elimination of the ester portion of the carboxylicacid ester group by an acid catalyst or the like produces a carboxylicacid group and confers alkali solubility, thus allowing formation of aresist pattern, and therefore the compositional ratio is a factorgoverning the resist resolution. As concerns the other carboxylic acidderivative group-containing triorganosiloxane portion (p), p ispreferably 0, but the value of p is not particularly restricted.

In formula 1 and formula 3, each R¹ is not particularly restricted solong as it is a monovalent organic group. A typical monovalent organicgroup is alkyl, and independent alkyl groups of 1-3 carbon atoms areparticularly preferred. Where R² is a direct bond, it is meant that thesymbol R² does not exist in the formulas. Where R² is a divalent organicgroup, it is not particularly restricted, and linear alkylene groups orcyclic alkylene groups of 1-10 carbon atoms, or combinations of suchlinear alkylene groups and cyclic alkylene groups, are preferred, amongwhich linear alkylene groups of 1-10 carbons are more preferred, andlinear alkylene groups of 1-3 carbon atoms are particularly preferred.Each R² may also be a different type of organic group mentioned above.R³ and R⁷ are not particularly restricted so long as they are monovalentorganic groups or organosilyl groups, and they are preferably ofdifferent types. Preferred as monovalent organic groups are alkyl groupsof 1-3 carbon atoms, and preferred as organosilyl groups aretriorganosilyl groups having alkyl groups of 1-3 carbon atoms. R⁸ is amonovalent organic group or organosilyl group, and is preferably afunctional group that is eliminated by acid generated by a photo-acidgenerator upon light exposure. As examples of such functional groupsthere may be mentioned triorganosilyl groups, t-butyl, tetrahydropyranyland 2-alkyladamantyl groups. Selection of these functional groups willbe determined based on the properties desired for the resist compositionthat includes the silicon-containing polymer of the invention, andmultiple different types may also be present depending on the need.

X represents hydrogen, a monovalent organic group or an organosilylgroup, none of which are restricted, and they may be of different types.Typical preferred monovalent organic groups include alkyl groups of 1-10carbon atoms and their substituted forms. Preferred as organosilylgroups are triorganosilyl groups including alkyl groups of 1-10 carbonatoms, alkenyl groups of 2-10 carbon atoms, aryl groups, haloalkylgroups or haloaryl groups. At least some of the X groups are preferablytriorganosilyl groups.

The silicon-containing polymer with the structure of formula 1preferably includes a triorganosilyl group with a photosensitivecrosslinkable group in at least some of the X groups, and particularlypreferred are polymers represented by formula 2 below wherein at leastsome of the X groups include a chloromethylphenylethyl-containingtriorganosilyl group as a photosensitive crosslinkable group

where R¹ represents a monovalent organic group, R² represents a directbond or a divalent organic group, R³ represents a monovalent organicgroup or an organosilyl group, any of which groups may be of differenttypes, X represents hydrogen, a monovalent organic group or anorganosilyl group, which groups may be of different types, R⁴, R⁵ and R⁶each independently represent a monovalent organic group, at least one ofwhich is a monovalent organic group including chloromethylphenylethyl,R⁴, R⁵ and R⁶ may be one or more different types of organic groups, k, land o are positive integers, m and n are 0 or positive integers, andthese subscripts satisfy the following relationship.$0 < \frac{o}{l + m + n + o} \leqq 0.8$

The silicon-containing polymer of the invention may also have anydesired silicon-containing polymer skeleton other than a tetrafunctionalsiloxane structure as represented by formulas 1-3, for example, askeleton with a trifunctional siloxane structure, difunctional siloxanestructure, silsesquioxane structure or polysilane structure, and it mayalso have a skeleton with a tetrafunctional siloxane structure asrepresented by formulas 1-3, as well as any desired two or moredifferent silicon-containing polymer skeletons.

The weight average molecular weight of the silicon-containing polymer ofthe invention is preferably in the molecular weight range of 1500 to1,000,000, and more preferably 3000-20,000, in terms of polystyrene. Ifthe molecular weight is lower than this range the heat resistance of theresist material is reduced, while if the molecular weight is above thisrange it will sometimes be unusable as a resist.

If necessary, a photo-acid generator or other compounds may be added tothe resist composition of the invention that contains as the maincomponent a silicon-containing polymer of the invention. As examples ofuseful photo-acid generators there may be mentioned onium salts such asdiphenyliodonium salts and triphenylsulfonium salts, sulfonic acidesters such as benzyl tosylate and benzyl sulfonate, andhalogen-containing organic compounds such as dibromobisphenol A andtris-dibromopropyl isocyanurate, but there is no restriction to these.The amount of photo-acid generator added is preferably 0.1-20 parts byweight to 100 parts by weight of the silicon-containing polymer, as asmaller amount may prevent practical photosensitivity and a largeramount may reduce the film quality or resolution. As other compounds tobe added, there may be mentioned surface active agents for improving thefilm formability, crosslinking agents for accelerating the crosslinkingof the silicon-containing polymers of formula 1 and formula 2,solubility-inhibiting agents for solubility contrast of thesilicon-containing polymer of formula 3 and amine-based compounds forimproving the stability of the film.

The resist composition of the present invention that contains, as themain component, a silicon-containing polymer of the invention having thestructure of formula 3 as the main structural unit becomes alkalisoluble when the functional group of RB in the silicon-containingpolymer is eliminated by an acid catalyst generated by the photo-acidgenerator upon light exposure; however, the elimination of thefunctional group may be accelerated by heating after the light exposure.

When forming a resist pattern using the resist composition of theinvention, a resist layer may be formed directly on a working substrateusing the resist composition of the invention, and the resist layersubsequently patterned by light exposure or development, to form thedesired resist pattern (single-layer resist method). Alternatively, afirst resist layer (lower layer resist) may be formed on a workingsubstrate, followed by formation of an upper resist layer using theresist composition of the invention, followed by patterning of the upperresist layer by light exposure and development, and etching of the lowerresist layer using the resulting upper pattern as a mask, to therebyform a resist pattern with a high aspect ratio, consisting of the upperpattern and the lower pattern (bi-layer resist method). The workingsubstrate used may be any substrate on which it is desired to form anintricate pattern using a photolithography method for manufacture of anelectronic device such as a semiconductor device, but the workingsubstrate is not limited to these.

The solvent used to form the resist composition of the invention may bean organic solvent such as propyleneglycol monomethylether acetate,n-butyl ether or methyl isobutyl ketone. The method of coating theresist composition of the invention onto the working substrate may bethe same method as used for coating of ordinary resist materials, andspin coating may be employed. The coating film thickness of the resistcomposition is preferably 0.01-1.0 μm, since a smaller thickness willresult in drastic dimensional variation during etching, and a largerthickness will lower the resolution. The film thickness is morepreferably 0.05-0.2 μm.

The material for the lower layer resist in the case of a bi-layer resistmethod may be an organic material, and it is preferred to use a novolacresin-based or vinylphenol resin-based commercially available resistmaterial, or a polyaniline-based or polythiophene-based conductivematerial. The lower resist layer is generally formed to a film thicknessof 0.1-10.0 μm, and more preferably has film thickness of 0.2-2.0 μm.

The light source used for exposure of the resist material of theinvention is preferably ultraviolet rays, a KrF excimer laser, an ArFexcimer laser, vacuum ultraviolet rays (VUV), extreme ultraviolet rays(EUV), X-rays, an electron beam, an ion beam or the like.

The alkali developing solution used for development of the resistmaterial of the invention may be a tetramethylammonium hydroxide (TMAH)aqueous solution, a potassium hydroxide aqueous solution, or the like.To either or both the developing solution and the rinsing solution ofwater there may be added alcohol or a surfactant to prevent patterndestruction or peeling.

According to the invention, a resist pattern may be easily formed bythis method. By using this resist pattern-forming method, it is possibleto fabricate LSIs, magnetic heads, liquid crystal devices, MCMs andother electronic devices, as well as photomasks.

Because the resist composition of the invention has the property ofwithstanding plasma etching by oxygen-containing gas, the resistcomposition of the invention may be used for the upper layer resist in abi-layer resist method to allow oxygen-reactive ion etching (O₂-RIE) foretching of the lower layer resist, and most preferably etching with amixed gas of oxygen and sulfur dioxide. The plasma etching apparatusused is preferably a high-density plasma etching apparatus.

The resist composition of the invention is suitable for formation ofresist patterns that require high aspect ratios, and therefore even incases, for example, where etching is difficult without the use of a hardmask, the etching can be carried out without using a hard mask, thusproviding the convenience that no steps are necessary for formation ofthe hard mask.

The present invention will now be explained in further detail by way ofthe following examples which, however, are in no way intended torestrict the scope of the invention.

EXAMPLE 1

In a nitrogen-flushed four-necked flask equipped with a reflux tube andthermometer there were placed 6.9 g (0.023 mole) of1,3-bis(carboxypropyl)tetramethyldisiloxane, 35 ml of purified water and20.6 ml of acetic acid, and the mixture was stirred and heated to 60° C.in an oil bath. After the dropwise addition of 12.48 g (0.06 mole) oftetraethoxysilane to the mixture over 30 minutes, reaction was conductedfor one hour. Next, 6.24 g (0.03 mole) of tetraethoxysilane was addeddropwise to the mixture over 30 minutes, and reaction was conducted for3 hours. After allowing it to cool to room temperature, the reactionsolution was transferred to a separatory funnel, 100 ml of water and 100ml of methyl isobutyl ketone (MIBK) were added to extract the solvent,and then the organic layer was filtered off with liquid layer separatingfilter paper, transferred to the four-necked flask and azeotropicallydrained to obtain an MIBK solution containing a tetrafunctional siloxanepolymer.

Next, in a nitrogen-flushed four-necked flask equipped with a refluxtube and thermometer there were placed the aforementioned polymer MIBKsolution and 0.8 ml of pyridine, and the mixture was heated to 68° C. inan oil bath. After dropwise addition of 2.68 g (0.011 mole) ofchloromethylphenylethyl dimethylchlorosilane to the mixture, reactionwas conducted for two hours. After allowing it to cool to roomtemperature, the precipitate was filtered, the solution was returned toa nitrogen-flushed four-necked flask equipped with a reflux tube andthermometer, 12.0 g (0.84 mole) of trimethylsilylimidazole was addeddropwise thereto while stirring at room temperature, and reaction wasconducted for 2 hours. After adding 18 ml of hydrochloric acid andfiltering off the resulting precipitate, the solution was transferred toa separatory funnel and rinsed 6 times with water, and then the organiclayer was filtered off with liquid layer separating filter paper andazeotropically drained. This solution was then concentrated and thecomponent that precipitated with hexane was lyophilized with dioxane toobtain a silicon-containing polymer with a molecular weight of 6800 anda dispersion degree of 1.35, at a 68% yield. The Si content of thepolymer was 35% as determined by NMR, and the values for therelationship in formula 1 based on the proportion of each functionalgroup were:$\frac{l}{l + m + n} = {{0.36\quad \frac{m}{l + m}} = 0.06}$

The transmittance of the polymer was 92% at 248 nm and 62% at 193 nm(both in terms of 0.1 μm).

The MIBK solution of this polymer was spin coated onto a Si wafer andbaked at 110° C. for 60 seconds to prepare a sample. Immersion in a2.38% TMAH aqueous solution exhibited a dissolution rate of 0.4 μm/s,thus confirming that the silicon-containing polymer was alkali soluble.

COMPARATIVE EXAMPLE 1

In a nitrogen-flushed four-necked flask equipped with a reflux tube andthermometer there were placed 9.2 g (0.02 mole) of1,3-bis(carboxypropyl)tetramethyldisiloxane, 84 ml of purified water,8.4 ml of concentrated hydrochloric acid and 320 ml of tetrahydrofuran(THF), and the mixture was heated to reflux in an oil bath. Afterdropwise addition of 12.5 g (0.06 mole) of tetraethoxysilane to themixture over 30 minutes, reaction was conducted for one hour. Themixture was cooled to room temperature and the reaction solution wasappropriately concentrated and then dissolved in an excess of MIBK.After transfer to a separatory funnel and rinsing with water until theaqueous layer became neutral, the organic layer was filtered off withliquid layer separating filter paper, transferred to the four-neckedflask and azeotropically drained to obtain a polymer MIBK solution. Thiswas concentrated to obtain a polymer that was then transferred to anitrogen-flushed four-necked flask equipped with a reflux tube andthermometer, and after adding 3.48 g of purified water, 1.23 ml ofconcentrated sulfuric acid and 12.42 g of THF and stirring, the mixturewas heated to reflux in an oil bath. After dropwise addition of 10.35 g(0.05 mole) of tetraethoxysilane to the mixture over 30 minutes,reaction was conducted for one hour. The mixture was cooled to roomtemperature and the reaction solution was appropriately concentrated andthen dissolved in an excess of MIBK. After transfer to a separatoryfunnel and rinsing with water until the aqueous layer became neutral,the organic layer was filtered off with liquid layer separating filterpaper, transferred to the four-necked flask and azeotropically drainedto obtain a polymer MIBK solution. The solution was concentrated toobtain a polymer that was then transferred to a nitrogen-flushedfour-necked flask equipped with a reflux tube and thermometer, and afteradding 90.00 g of MIBK and 0.28 g of pyridine and stirring, the mixturewas heated to 70° C. in an oil bath. After dropwise addition of 0.96 g(0.004 mole) of chloromethylphenylethyl dimethylchlorosilane to themixture, reaction was conducted for two hours. After allowing to cool toroom temperature, the solution was naturally filtered and theprecipitate was removed. The solution was returned to thenitrogen-flushed four-necked flask equipped with a reflux tube andthermometer, 8.0 g (0.056 mole) of trimethylsilylimidazole was addeddropwise thereto while stirring at room temperature, and reaction wasconducted for 2 hours. After adding 12 ml of hydrochloric acid andnaturally filtering the resulting precipitate, the solution wastransferred to a separatory funnel and rinsed with water until theaqueous layer became neutral, and the organic layer was filtered offwith liquid layer separating filter paper, transferred to thefour-necked flask and azeotropically drained. This solution was thenconcentrated, and the high molecular weight component was separated withtoluene and lyophilized with dioxane to obtain a silicon-containingpolymer with a molecular weight of 8000 and a dispersion degree of 1.7,at a 40% yield. The Si content of the polymer was 35% as determined byNMR, and the values for the relationship in formula 1 based on theproportion of each functional group were:$\frac{l}{l + m + n} = {{0.45\quad \frac{m}{l + m}} = 0.32}$

The transmittance of the polymer was 80% at 248 nm and 42% at 193 nm(both in terms of 0.1 μm).

The MIBK solution of this polymer was spin coated onto a Si wafer andbaked at 110° C. for 60 seconds to prepare a sample. Immersion in a2.38% TMAH aqueous solution exhibited a very high dissolution rate, thusconfirming that the silicon-containing polymer was alkali soluble.

EXAMPLE 2

A resist solution was prepared by dissolving the silicon-containingpolymer of Example 1 in MIBK. Next, a novolac resin-based solution wasfirst spin coated onto a Si wafer and baked for 30 minutes with a hotplate at 250° C. to form a 0.45 μm lower resist layer, and then a resistsolution of the silicon-containing polymer of Example 1 prepared abovewas spin coated onto the lower layer resist and prebaked at 110° C. for60 seconds to form a 0.1 μm upper resist layer. After exposing the upperlayer with an ArF excimer laser, it was developed with a 2.38% TMAHaqueous solution. This resulted in resolution of a 0.17 μmline-and-space pattern at an exposure dose of 35 mJ/cm². Upon etchingwith a parallel plate RIE apparatus under conditions of 0.16 W/cm² RFpower, 10 sccm oxygen flow rate and 10 mTorr gas pressure, the lowerlayer was successfully transferred without shape deterioration, thusallowing formation of a bi-layer resist pattern with an aspect ratio ofabout 3. Measurement of the etching rate of the upper layer resist madeof the silicon-containing polymer, with respect to the lower layerresist, revealed a high O₂-RIE resistance of approximately 100-fold.Upon heating the pattern-formed substrate on a hot plate and determiningthe heat resistance of the resist pattern, absolutely no changes in thepattern shape were found even with heating at 300° C. and above.

EXAMPLE 3

A 0.45 μm lower resist layer was formed on a Si wafer in the same manneras Example 2, and then a resist solution comprising an MIBK solution ofthe silicon-containing polymer of Example 1 was spin coated thereon andprebaked at 110° C. for 60 seconds to form a 0.1 μm upper resist layer.After exposure of the upper layer with an ArF excimer laser using aLevenson phase contrast shift mask, it was developed with a 2.38% TMAHaqueous solution. This resulted in resolution of a 0.14 μmline-and-space pattern at an exposure dose of 35 mJ/cm². Upon etchingwith a parallel plate RIE apparatus under conditions of 0.16 W/cm² RFpower, 10 sccm oxygen flow rate and 10 mTorr gas pressure, the lowerlayer was successfully transferred without shape deterioration, thusallowing formation of a bi-layer resist pattern with an aspect ratio ofabout 3.6.

EXAMPLE 4

A 0.45 μm lower resist layer was formed on a Si wafer in the same manneras Example 2, and then a resist solution comprising an MIBK solution ofthe silicon-containing polymer of Example 1 was spin coated thereon andprebaked at 110° C. for 60 seconds to form a 0.1 μm upper resist layer.After exposure of the upper layer with an electron beam, it wasdeveloped with a 2.38% TMAH aqueous solution. This resulted inresolution of a 0.1 μm line-and-space pattern at an exposure dose of 70μC/cm². Upon etching with a parallel plate RIE apparatus underconditions of 0.16 W/cm² RF power, 10 sccm oxygen flow rate and 10 mTorrgas pressure, the lower layer was successfully transferred without shapedeterioration, thus allowing formation of a bi-layer resist pattern withan aspect ratio of about 5.0.

COMPARATIVE EXAMPLE 2

A resist solution was prepared by dissolving only the silicon-containingpolymer of Comparative Example 1 in MIBK. Next, a novolac resin-basedsolution was spin coated onto a Si wafer and baked for 30 minutes with ahot plate at 250° C. to form a 0.45 μm lower resist layer. Next, theresist solution prepared above was spin coated onto the lower layerresist and prebaked at 110° C. for 60 seconds to form a 0.1 μm upperresist layer. After exposure of the upper layer with an ArF excimerlaser, it was developed with a 2.38% TMAH aqueous solution. Thisresulted in separate resolution of no smaller than a 0.5 μmline-and-space pattern, while dissolution was to 0.4 μm and smaller.When a 0.0238% TMAH aqueous solution was used as the developingsolution, a 0.2 μm line-and-space pattern was resolved.

EXAMPLE 5

A polymer was synthesized in the same manner as Example 1, except thatthe charging amount of the 1,3-bis(carboxypropyl)tetramethyldisiloxanewas changed. As a result there were obtained polymers with weightaverage molecular weights of 13,000 and 3000. The values for therelationship between the numbers in formula 1 for the polymers asdetermined by NMR, were$\frac{l}{l + m + n} = {{0.18\quad \frac{m}{l + m}} = 0.05}$

for the 13,000 molecular weight polymer and$\frac{l}{l + m + n} = {{0.36\quad \frac{m}{l + m}} = 0.05}$

for the 3000 molecular weight polymer, and both were within the rangesfor the specific proportions.

EXAMPLE 6

The 3000 molecular weight silicon-containing polymer obtained in Example5 was used alone as an upper layer resist polymer, and it was evaluatedas a resist material in the same manner as Example 2. After exposure ofthe upper layer with an ArF excimer laser, it was developed with a 2.38%TMAH aqueous solution. This resulted in resolution of a 0.17 μmline-and-space pattern at an exposure dose of 45 mJ/cm². Upon etchingwith a parallel plate RIE apparatus under conditions of 0.16 W/cm² RFpower, 10 sccm oxygen flow rate and 10 mTorr gas pressure, the lowerlayer was successfully transferred without shape deterioration, thusallowing formation of a bi-layer resist pattern with an aspect ratio ofabout 3. Measurement of the etching rate of the upper layer resist madeof the silicon-containing polymer, with respect to the lower layerresist, revealed a high O₂-RIE resistance of approximately 100-fold.Upon heating the pattern-formed substrate on a hot plate and determiningthe heat resistance of the resist pattern, absolutely no changes in thepattern shape were found even with heating to 300° C. and above.

EXAMPLE 7

A mixture of two silicon-containing polymers with different molecularweights obtained according to Example 5 was used as an upper layerresist polymer (13,000 molecular weight polymer:3000 molecular weightpolymer=5:95 (wt ratio)), and it was evaluated as a resist material inthe same manner as Example 2. After exposure of the upper layer with anArF excimer laser, it was developed with a 2.38% TMAH aqueous solution.This resulted in resolution of a 0.15 μm line-and-space pattern at anexposure dose of 25 mJ/cm². Upon etching with a parallel plate RIEapparatus under conditions of 0.16 W/cm² RF power, 10 sccm oxygen flowrate and 10 mTorr gas pressure, the lower layer was successfullytransferred without shape deterioration, thus allowing formation of abi-layer resist pattern with an aspect ratio of about 3.3. Measurementof the etching rate of the upper layer resist made of thesilicon-containing polymer, with respect to the lower layer resist,revealed a high O₂-RIE resistance of approximately 100-fold. Uponheating the pattern-formed substrate on a hot plate and determining theheat resistance of the resist pattern, absolutely no changes in thepattern shape were found even with heating to 300° C. and above.

EXAMPLE 8

In a reflux tube-equipped Erlenmeyer flask there were placed 3.0 g ofthe silicon-containing polymer with a molecular weight of 6800 and adispersion degree of 1.35 obtained in Example 1, 30 ml of dioxane and acatalytic amount of p-toluenesulfonic acid, and the mixture was stirredand heated to 60° C. in an oil bath. After the dropwise addition of12.48 g (0.06 mole) of dihydropyrane to the mixture, reaction wasconducted while observing the esterification rate by IR. The reactionsolution was then purified by dropwise addition to a water/methanolmixture and reprecipitation. The polymer was transferred to the refluxtube-equipped Erlenmeyer flask as a mixed solution with 25 ml of MIBKand 5 ml of methanol and stirred, and then 6 ml of a 10 wt % hexanesolution of trimethylsilyldiazomethane was added dropwise and reactionwas conducted at room temperature for one hour. Ether was then added tothe reaction solution, and this mixture was transferred to a separatoryfunnel, rinsed 6 times with water, dewatered by addition of magnesiumsulfate to the ether layer, and then filtered to obtain the targetpolymer solution. This was then concentrated and lyophilized withdioxane to obtain a silicon-containing polymer with a molecular weightof 6000 and a dispersion degree of 1.4. The Si content of the polymerwas 34% as determined by NMR, and the values for the relationship informula 3 based on the proportion of each functional group were:$\frac{l}{l + n + p + q} = {{0.03\quad \frac{q}{l + n + p + q}} = 0.52}$

The transmittance of the polymer was 76% at 248 nm and 54% at 193 nm(both in terms of 0.1 μm).

The MIBK solution of this polymer was spin coated onto a Si wafer andbaked at 110° C. for 60 seconds to prepare a sample. Immersion in a2.38% TMAH aqueous solution exhibited no dissolution of the polymer,thus confirming that the silicon-containing polymer was alkaliinsoluble.

EXAMPLE 9

A 0.45 μm lower resist layer was formed on a Si wafer in the same manneras Example 2, and then a resist solution, comprising an MIBK solutionprepared by dissolving the silicon-containing polymer of Example 8 andtriphenylsulfonium triflate in an amount of 5 parts by weight to 100parts by weight of the silicon-containing polymer in MIBK, was spincoated thereon and prebaked at 110° C. for 60 seconds to form a 0.1 μmupper resist layer. After exposure of the upper layer with an ArFexcimer laser, it was developed with a 2.38% TMAH aqueous solution. Thisresulted in resolution of a 0.14 μm hole pattern at an exposure dose of10 mJ/cm². Upon etching with a parallel plate RIE apparatus under thesame conditions as Example 3, the lower layer was successfullytransferred without shape deterioration, thus allowing formation of abi-layer resist pattern with an aspect ratio of about 4.5. The etchingrate of the upper layer resist made of the silicon-containing polymer,with respect to the lower layer resist, was approximately 90-fold. Uponheating the pattern-formed substrate on a hot plate and determining theheat resistance of the resist pattern, absolutely no changes in thepattern shape were found even with heating to 300° C. and above.

EXAMPLE 10

A 0.15 μm line-and-space resist pattern was formed on a substratelaminated with films of chromium oxide, pure chromium and chromium oxidein that order, according to the method described in Example 3. Theobtained resist pattern was used as a mask for etching of the underlyingchromium using reactive gas containing a halogenated hydrocarbon addedto oxygen, and then the two-layer resist was released to produce areticle.

A quartz substrate laminated with a chromium oxide film and MeSiON filmwas used as a half-tone material in place of the chromium oxide/purechromium/chromium oxide film for patterning in the same manner, tomanufacture a half-tone reticle.

EXAMPLE 11

A MOS transistor 10 with elements isolated by field oxidation was formedon a silicon substrate 1. A dielectric layer 21 was accumulated on thegate electrode 11 of the MOS transistor, and an opening for feeding awire to the gate electrode 11 was formed by lithographic means. A thinfilm 31 was then formed of titanium nitride (TiN) used as a barriermetal, and a thin film 32 of Al was accumulated thereover as a wiringmaterial (FIG. 1). For working of the Al/TiN film into a wiring pattern,a resist pattern 42 acting as an etching mask was formed on the Al/TiNaccumulated layer film by the means described in Example 2. The resistpattern was used as an etching mask for transfer to the lower layer byoxygen plasma etching (FIG. 2). The resist pattern 42 was removed byfluorine-based plasma etching, to complete an etching mask 41 comprisingthe lower layer resist. The etching mask 41 was used for etching of theAl/TiN accumulated layer film to be etched, by chlorine-based plasma,giving a gate wiring pattern with a high aspect ratio (FIG. 3).

EXAMPLE 12

After forming a lower shield, lower gap, lead element, terminal, uppergap, upper shield, coil, insulating film and plating base on an AlTiCsubstrate by publicly known methods, a 0.25 μm resist pattern was formedthereover by the method described in Example 7. The obtained resistpattern was then used as a mask for etching of the underlayer, afterwhich an upper magnetic material was formed as a film thereover by aplating method, and the resist was released to form an upper electrode.

As the above explanation demonstrates, the silicon-containing polymer ofthe invention, having carboxylic acid groups and functional groups in aspecific proportion, is simple to produce, exhibits an excellentshelf-life, and is suitable as a resist material that can be easilydeveloped with common alkali developing solutions, and whichsimultaneously provides high sensitivity, high resolution, high O₂-RIEresistance and high heat resistance; resist compositions of theinvention comprising such a silicon-containing polymer are expected tomake a major contribution to the more intricate and multilayered wiringsthat will accompany ever higher integration and higher functionality ofelectronic devices such as semiconductor devices.

What is claimed is:
 1. A method of forming a resist pattern, said methodcomprising: (1) forming at least one resist layer on a working substrateby coating the working substrate with a resist composition, the resistcomposition comprising a silicon containing polymer which comprises as amain structural unit a structure represented by formula 1:

 where R¹ represents a monovalent organic group; R² represents a directbond or a divalent organic group; R³ represents a monovalent organicgroup or an organosilyl group, any of which groups may be of differenttypes; X represents hydrogen, a monovalent organic group or anorganosilyl group, which groups may be of different types; k and l arepositive integers; m and n are 0 or positive integers, and thesesubscripts satisfy the following relationship:$0 < \frac{1}{1 + m + n} \leqq {0.8\quad 0} \leqq \frac{m}{1 + m} < 0.2$

(2) exposing the resist layer to light and developing the resist layerso as to form a resist pattern.
 2. The method according to claim 1,comprising etching a lower resist layer by oxygen-reactive ion etching(O₂-RIE).
 3. The method according to claim 1, comprising etching a lowerresist layer with a plasma etching apparatus which is a high-densityplasma etching apparatus.
 4. The method according to claim 1, wherein atleast one of the X groups is a triorganosilyl group.
 5. The methodaccording to claim 1, wherein the triorganosilyl group includes at leastone photosensitive crosslinkable group.
 6. The method according to claim5, wherein the photosensitive crosslinkable group ischloromethylphenylethyl, and wherein the silicon containing polymercomprises as a main structural unit a structure represented by formula2:

where R¹ represents a monovalent organic group, R² represents a directbond or a divalent organic group, R³ represents a monovalent organicgroup or an organosilyl group, any of which groups may be of differenttypes, X represents hydrogen, a monovalent organic group or anorganosilyl group, which groups may be of different types, R⁴, R⁵ and R⁶each independently represent a monovalent organic group, at least one ofwhich is a monovalent organic group including chloromethylphenylethyl,k, l and o are positive integers, m and n are 0 or positive integers,and these subscripts satisfy the following relationship:$0 < \frac{O}{l + M + N + O} \leq {0.8.}$


7. A method of forming a resist pattern, said method comprising: (1)forming a lower resist layer on a working substrate by coating theworking substrate with a first resist material; (2) forming an upperresist layer over the lower resist layer by coating with a second resistmaterial, the second resist material comprising a resist compositionwhich comprises a silicon-containing polymer having as a main structuralunit a structure represented by formula 1:

 where R¹ represents a monovalent organic group; R² represents a directbond or a divalent organic group; R³ represents a monovalent organicgroup or an organosilyl group, any of which groups may be of differenttypes; X represents hydrogen, a monovalent organic group or anorganosilyl group, which groups may be of different types; k and l arepositive integers; m and n are 0 or positive integers, and thesesubscripts satisfy the following relationship:$0 < \frac{1}{1 + m + n} \leqq {0.8\quad 0} \leqq \frac{m}{1 + m} < 0.2$

(3) exposing the upper resist layer to light and developing the upperresist layer so as to pattern the upper resist layer; (4) etching thelower resist layer with the resulting upper layer pattern as a mask soas to form a resist pattern.
 8. The method according to claim 7,comprising etching the lower resist layer by oxygen-reactive ion etching(O_(2 -RIE).)
 9. The method according to claim 7, comprising etching thelower resist layer with a plasma etching apparatus which is ahigh-density plasma etching apparatus.
 10. A method of fabricating anelectronic device, said method comprising forming a resist patternthrough the method according to any one of claims 1 or
 7. 11. A methodof fabricating a photomask, said method comprising forming a resistpattern through the method according to any one of claims 1 or
 7. 12.The method according to any one of claims 1 or 7, wherein R² is—(CH₂)_(a)— and a is an integer of 1-10.
 13. A method of forming aresist pattern, said method comprising: (1) forming at least one resistlayer on a working substrate by coating the working substrate with aresist composition, the resist composition comprising a siliconcontaining polymer which comprises as a main structural unit a structurerepresented by formula 3:

 where R¹ represents a monovalent organic group, R² represents a directbond or a divalent organic group, R⁷ and R⁸ each independently representa monovalent organic group or an organosilyl group, any of which groupsmay be of different types, X represents hydrogen, a monovalent organicgroup or an organosilyl group, which groups may be of different types, kand q are positive integers, l, n and p are 0 or positive integers, andthese subscripts satisfy the following relationship:$0 \leqq \frac{l}{l + n + p + q} < {0.5\quad 0.1} < \frac{q}{l + n + p + q} \leqq 0.8$

 and (2) exposing the resist layer to light and developing the resistlayer so as to form a resist pattern.
 14. The method according to claim1, wherein at least one of the X groups is a triorganosilyl group. 15.The method according to claim 13, wherein R⁸ is a functional group thatis eliminated by an acid catalyst.